The invention relates to an oil-in-water emulsion for cold rolling light metals, in particular aluminum and its alloys wherein the said emulsion contains a reaction layer former, polyethoxylated sorbitanoleates as emulsifier, unsaturated, long chain monocarboxylic acids as inhibitor against hydrogen embrittlement and rusting, hexamethylenetetramine as stabilizer, fungicide and bactericide and deionized water as the balance.
Compared with oil-based rolling lubricants oil-in-water emulsions provide much better cooling due to the high heat of vaporization of water. Consequently they permit greater reductions per pass and/or higher rolling speeds. Besides these purely economic factors, which help considerably to achieve better efficiency, it must be mentioned that aqueous rolling lubricants also markedly reduce the problems of waste gases and fumes and are less depedent on mineral oil. The light metal industries, in particular the aluminum industry, have therefore already carried out many trials to enable oil-in-water emulsions to be employed for cold rolling strip materials.
From the German Auslegeschrift No. 26 32 142 an oil-in-water emulsion for cold rolling light metals is known and contains alkylmonocarboxylic acid esters as reaction layer former, polyisobutylene as hydrodynamic film former, polyethoxylated sorbitanoleate as emulsifier, unsaturated, long chain monocarboxylic acids as inhibitor against hydrogen embrittlement and rusting, hexamethylenetetramine as stabilizer, fungicide and bactericide, balance deionized water.
With the emulsion from the German Auslegeschrift No. 26 32 142 it was in fact possible to achieve reductions of close to 90% with aluminum. However, the poorer surface quality produced by the high reductions per rolling pass did not always meet the requirements made of strip and foil surfaces.